GROUSE DISEASE 209 



to form four smaller spores inside. The spores 

 are scattered over the moors by the action of 

 the wind and rain, and, alighting on the heather 

 or in the tarns of the moors, are taken up by 

 the grouse in their food or drink. When the 

 cysts are swallowed, they enter the gizzard of 

 the bird and pass unchanged into the first part 

 of the intestine, called the duodenum. Here the 

 pancreatic juice is poured into the intestine, to 

 aid in digestion, and under its influence the 

 cyst-wall is softened and dissolved, and the four 

 small spores (contained within the ripened spore 

 or oocyst) are set at liberty. Each small spore 

 contains two active motile germs or sporozoites, 

 which emerge from the softened spore-case, and 

 proceed to penetrate the epithelium of the duo- 

 denum. The young parasites ultimately cause 

 the destruction of the lining of the first part of 

 the small intestine the region where, normally, 

 the most active digestive processes occur. The 

 coccidium parasites multiply in the duodenal 

 epithelium, and then invade the caeca or " blind- 

 guts," with disastrous results. 



Sooner or later a limit is reached, on the one 

 hand, to the power of the grouse-chick to provide 

 nourishment for the parasites, and on the other 



